The invention relates to an improvement in products combining television and video recorder.
Combos are products comprising a display, e.g. a cathode ray tube (CRT) and a video recorder, e.g. a video tape recorder (VTR). A video recorder should be understood as any device capable of recording video signals on an appropriate storage medium, e.g. magnetic tape, optical disk, magneto-optical disk, magnetic hard disk. In order to reduce their cost, some combos are fit with only one video circuit which is used by both the television and the video recorder.
In some combos, the video circuit controls the level of its output signals directed to the display thanks to a feedback loop using a feedback signal from the display. An example of such a construction is given in German patent application No. 33 37 106. Such video circuits are said to have an auto-cutoff function.
Combos conventionally function according to three possible operating modes: an xe2x80x9conxe2x80x9d mode wherein both the display and the video recorder are switched on, a mode called xe2x80x9cstandby recordingxe2x80x9d wherein the display is switched off and the video recorder is switched on and an xe2x80x9coffxe2x80x9d mode in which both the display and the video recorder are switched off.
In conventional combos with a single video circuit and the auto-cutoff function, a very bright image is displayed when switching the combo from the standby recording mode to the on mode.
The invention seeks to avoid displaying such a bright image which is uncomfortable to the user by simple and cheap means.
An apparatus according to the invention comprises a source of video signal, a video circuit connected to the source and generating at least a first signal and a second signal, a video recorder for recording the second signal on a medium and a display comprising an amplifier for the first signal and displaying images coded in the first signal.
The video circuit includes calibration means for adjustment of the first signal depending on a feedback signal from the display.
A control signal is generated when the video recorder is functioning and when the display is switched on and an amplification control circuit progressively revives the amplifier after the control signal is generated.
According to other features of the invention, the amplification control circuit generates a biasing voltage of the amplifier. The amplification control circuit includes a RC-circuit able to continuously vary the biasing voltage between a first voltage and a second voltage during a period of time, which is preferably longer than 1 s.
The calibration means includes a feedback loop comprising a multiplier and a black level clamp which calibrate the first signal depending on the feedback signal. Practically, the first signal is a set of three signals in R,G,B form.
The control signal is generated by a controller connected to the amplification control circuit, more specifically upon receipt of a signal from a remote-control or from a keyboard. The control signal is representative of a mode of the apparatus.
The invention is thus about a video apparatus comprising a display comprising an amplifier having an input, a controller having an output generating a signal representative of a mode of the apparatus, and an amplification control circuit connected to said output and being able to generate on said input a voltage continuously varying between a first voltage and a second voltage during a period of time.
The progressive revival of the amplifier allows the feedback loop of the calibration circuit to adjust during the period of time and the video circuit to output calibrated signals when full amplification is realized by the amplifier.
The first images which are displayed after switching to the on-mode are thus slightly amplified and, when the amplification has reached a normal value, the feedback loop is fully efficient and the brightness of the image is conveniently regulated.
Hence no very bright image will appear when the combo is switched from the standby recording mode to the on mode.